A LARGE MULTIGENE FAMILY EXPRESSED DURING THE ERYTHROCYTIC SCHIZOGONYOF PLASMODIUM-FALCIPARUM

We report the identification of a large multigene family of Plasmodium falciparum using a clone isolated with a polyclonal antiserum raised to a Babesia divergens merozoite protein. The recombinant antigen reac ted with human sera collected from individuals exposed to malaria. The deduced protein sequence contains a motif homologous to the consensus sequence of merozoite rhoptry proteins encoded by multigene families in several Babesia species. Antibodies raised to the recombinant prote in reacted with a 60-kDa merozoite protein both on B. divergens and on P. falciparum immunoblots. The insert hybridized to a large number of fragments on P. falciparum Southern blots and to most chromosomes of the parasite. Specifically, approx. 3-kb RNAs were detected in 4-16-nu cleus schizonts. Ten distinct cDNAs were isolated that differed in the size, position and number of restriction sites in the region homologo us to the original genomic clone. With about 140 copies per haploid ge nome, this is the first large multigene family described in malaria pa rasites. The existence of a multigene family encoding proteins present in the invasive stage of malaria parasites suggests an important role in invasion and denotes a significant potential for generating divers ity.